Climate and land‐use change severity alter trait‐based responses to habitat conversion

Aim A major goal in modern ecology is understanding the source of variation in species responses to anthropogenic change. Trait‐based approaches show promise, but traits found to be predictive in one study often fail in others. We seek to understand whether variation in traits’ explanatory power comes about due to interaction effects—between multiple traits and between traits and the environment. We assess the context‐dependence of trait‐based responses to habitat conversion by testing the hypothesis that abundance in converted habitats decreases with arboreality, while including interactions with reproductive mode, a trait of known importance, and biologically relevant climate variables. Location Global tropical forest biomes. Time period 1997–2018. Major taxa studied Amphibians. Methods Using 18 studies of amphibian communities from across the globe, we evaluate the role of vertical niche position and reproductive mode in determining abundance within primary forest, structurally complex agriculture, and structurally simple agriculture. We examined interactions between traits, land‐use types and climate variables. Results Average abundance steadily declined from primary forest, through complex agriculture, and was lowest in simple agriculture. Arboreality (high vertical niche position) leads to increased sensitivity to conversion of forest to simple agriculture, while terrestrial species are more sensitive when habitat is converted to complex agriculture. We found no evidence that trait‐by‐trait interactions determined abundance after habitat conversion. However, the effects of climate can alter how species’ traits determine abundance patterns—while lentic amphibians maintain abundance after conversion regardless of climate zone, direct developers and lotic species become increasingly sensitive to habitat modification in warmer climates. Major conclusions Vertical niche position acts as a limiting axis in modified environments, with response to conversion dependent on the availability of vegetative strata. Interactions between traits and the environment play a strong and underappreciated role in defining community composition in converted habitats. Such interactions may underlie the difficulties past studies have had in achieving generality across study locations and faunas.